Maize Performance and Soil Moisture Retention Under Inoculated Cowpeas Intercrop in Meru and Tharaka Nithi Counties

Abstract

Agriculture is the main source of livelihood in Kenya with maize being produced in diverse environments. However, in Meru and Tharaka Nithi counties, small holder maize productivity has been diminishing due to declining soil fertility and frequent droughts. Nitrogen (N) is the principal nutrient limiting maize production hence the need for intercropping using cowpeas that are inoculated with the correct exotic bacterial strain that fix N in the soil. There was need to assess N fixation capacity using exotic bacteria by inoculating cowpeas with the correct bacterial strain. The use of N fixing legumes in intercrops with cereal crops remains a cheaper and viable option available for the resource constrained farmers to enhance soil fertility. The objective of the study was to contribute towards improved maize performance through rhizobium inoculated cowpeas intercropping. The study was conducted at two locations i.e. Kenya Agricultural Livestock Research Organization (KALRO) Igoji substation and Magutuni secondary school in Meru and Tharaka Nithi counties respectively, during the long rains of the year 2018. The experiment was laid out in a Randomized Complete Block Design and replicated three times. The treatments included maize hybrid Duma 43 variety sown as a sole crop (TI); Rhizobium inoculated variety K80, cowpeas maize intercrop (T2), cowpeas maize intercrop without inoculation (T3) and non-inoculated cowpeas K80 sole crop (T4). Data collected on maize included plant height, stem girth, canopy cover, leaf area index, light extinction coefficient and yield. Data collected on cowpea was yield. Moisture retention capacity was determined by use of a neutron probe after every week by recording the moisture from the soil in millimeters up to grain filling. Soil samples for N analysis were taken before planting and after harvesting on each treatment plot basis and the homogenous sample analyzed at University of Nairobi (UoN) soil chemistry laboratory. A general linear model was performed and data subjected to analysis of variance (ANOVA) using GENSTAT statistical package (VSN International, 2011). Means were separated using Fischer’s protected least significant difference (LSD) at 5% probability level. Results indicated that intercropped patterns under inoculated cowpeas recorded a greater leaf area index of 3.75 at Igoji and 3.16 at Magutuni. Light extinction coefficient was high in intercrops than in sole stands and ranged between 0.52 and 0.34 at Igoji and between 0.57 and 0.37 at Magutuni. Intercropped patterns intercepted more photosynthetically active radiation (PAR) (581.54 MJm-2) than pure stands (88.35 MJm-2). At kernel development stage, significantly higher soil moisture content was observed under intercropping patterns T2, (255.5±3.7mm, 253.0±1.9mm) and T3, (250.7±2.9mm, 240.5±1.3mm) than in pure maize stand T1, (245.3±4.0mm, 230.8±2.7mm) and sole cowpeas T4, (248.9±5.6mm, 233.7±3.7mm) in Igoji and Magutuni, respectively. Nitrogen fixed in T2, (0.20 g/kg, 0.18 g/kg) was higher than in T3, (0.18 g/kg, and 0.17 g/kg) and T4, (0.19 g/kg, 0.17 g/kg) at Igoji and Magutuni respectively and this was attributed to the effect of inoculation in cowpeas. The results of this study underpins the importance of intercropping maize with inoculated cowpeas as a cheaper soil fertility improvement method and as a moisture retention strategy for resource poor farmers in Meru and Tharaka Nithi counties.